The efficiency of gas turbine engines is dependent, in part, on the ability of engine components to confine the motive fluids, such as air and products of combustion, to intended pathways. Leakage from such design flowpaths can reduce efficiency. Accordingly, designers of gas turbine engines have reported a variety of sealing arrangements to reduce or control such leakage. One type of arrangement includes closely spaced, juxtaposed rotary seal members, one surface of which is harder than, or more abrasive to, the opposing member surface. Upon relative thermal expansion of such surfaces, tending to close the space between them into an abrasive or galling condition, the harder surface will remove a portion of the opposing surface to approach a "zero clearance" condition. Sometimes the abrading surface includes embedded abrasive particles.
One example of such a sealing arrangement is at the tip portion of a blading member, rotating relative to an opposing shroud. Some gas turbine engine compressors have used titanium alloy blading members which, as a result of rubbing on a shroud, have produced titanium alloy ignition from heat generated by friction. Therefore, it is important, in such an arrangement, to provide appropriate abrasion to control clearance yet dissipate friction heat to a point below the ignition point of the member surface portions of such a seal. Also, it is important to retain abrasive particles, when used, upon the surface of the abrading member by a means which is metallurgically and thermally stable to enhance integrity of the arrangement.